The present application is directed towards raiser seats for assisting a person from a sitting to a standing position. It is particularly applied to raiser seats in which the motion of the seat is determined by cams.
A variety of seats which can be raised or lowered in order to assist people from a sitting to a standing position are known. These are applied in many fields, and are of particular use in recovery from operations or for people with limited abilities. These seats may be a simple chair, or may also be used in medical transfer chairs, commodes or wheelchairs.
An example of a raiser seat is discussed U.S. Pat. No. 5,513,867 (Bloswick et al). This patent relates to a seat-lift wheelchair. The seat can pivot about its front edge to assist a person in standing up. The lift of the seat is achieved by the action of a tension spring pulling on a cable. The cable acts around a cam attached to the bottom of the seat. This cam determines the effective distance of the tension in the cable from the pivot point in the seat. It therefore allows the torque to be varied depending on the position of the seat.
This mechanism requires a large tension spring in order to generate the required torque. It will also only function correctly when the pivot point of the seat is fixed relative to the seat frame and the tension spring.
The present invention provides a raiser seat in which the seat rests upon cams which are attached to the seat frame. These cams can be rotated to lift the seat.
According to a first aspect of the present invention, there is provided a raiser seat for assisting a person from a sitting to a standing position comprising:                a seat frame;        a seat adapted for movement relative to the seat frame between a lowered position and a raised position; and        a movement mechanism for moving the seat between the lowered and the raised positions;        wherein the movement mechanism comprises at least one cam and wherein the seat is supported by the at least one cam such that rotation of the at least one cam results in movement of the seat relative to the seat frame.        
The term “cam” includes single and multiple bladed and lever-type cams. Lever-type cams can have one or more tracks, conveyers, rollers/casters/wheels, roller type or plain bearings, or linear slides that act to set the effective profile of the lever, thus achieving the same function as a cam.
Unlike U.S. Pat. No. 5,513,867, the seat is supported by the cam, rather than the cam being fixed to or part of the seat. This means that rotation of the cam causes the seat to move. During this movement there can be relative movement between the seat and the cam. The profile of the lift (including tilt and/or translation) can be determined according to the profile of the cam. In this way the cam is directly responsible for movement of the seat, rather than being indirectly responsible for movement of the seat due to the action of a tension cable as in U.S. Pat. No. 5,513,867.
Preferably, the seat forms part of a seat unit. This allows the seat to be permanently or removably attached to the seat frame, depending on the particular application.
Preferably, the at least one cam is retained within the seat unit. Thus, the seat and cam can easily be incorporated into a finished seat unit. It also has the advantage that the seat unit can be changed to allow different cam profiles to be used with the same seat frame. In one embodiment, the at least one cam is rotatably fixed to the seat unit.
Preferably the seat unit comprises at least one reinforcing element. The reinforcing element acts to increase the rigidity, strength, and general practicalities of the seat unit.
Preferably the seat and/or seat unit can be mounted on the seat frame by sliders in one embodiment. Protrusions and/or invasions (grooves) of different shapes and forms for location of the seat and/or seat unit can also be used. The seat and/or seat unit can be horizontally or vertically slid or placed in positions. Locking mechanisms can also be provided.
Preferably, the movement mechanism comprises a pair of coaxial cams. These cams can be located on either side of the seat and therefore spread the load of a person sitting on the seat evenly between them.
Preferably, the movement mechanism comprises a first pair of coaxial cams located supporting a rear end of the seat and a second pair of coaxial cams supporting a front end of the seat. By using two pairs of cams, one towards the rear and one towards the front, the lift profile can be varied almost infinitely. The profiles of the cams will determine the movement profile of the seat. This can vary considerably, because the use of cams means that a fixed pivot point is not required.
Preferably, the raiser seat further comprises a motor for rotating the at least one cam. The motor can be located anywhere within raiser seat, and may be contained in a separate detachable casing. For example, it can be side-by-side, above or below the cam, or contained within the seat unit. The motor may drive the cam directly or indirectly. With an indirect drive various drive transfer components can be used, including drive couplings and meshed gears. If the motor drives the cam indirectly, the power transfer components can be chosen to allow the drive to be transferred from wherever the motor is located. Furthermore the drive transfer components can be also be chosen to alter the characteristics of the mechanism, for example the torque or rotational speed. The motor can be controlled via a control box for all required operational parameters.
Preferably, the at least one cam is attached to a coaxial gear in meshed engagement with a rack such that translation of the rack results in rotation of the at least one cam.
Preferably, the rack is driven by a gear powered by a motor.
Preferably, the profile of the at least one cam is chosen dependent on the path followed by the seat as it moves between the first and second position. This allows the motion of the seat to be tailored to specific purposes by the choice of cam profile. Thus, for example, the combination of lift, tilt and cycle time/speed of operation of the seat can be varied as required for a particular application. Alternatively, a set of predetermined cams and/or control programs can be provided giving a range of common movement profiles.
Preferably, the movement mechanism further comprises at least one actuator fixed at a first end to the seat. In one embodiment a second end of the actuator is fixed to either the seat frame or the seat unit, and the second end can move relative to the first end in a generally vertical direction. An actuator is a simple way of achieving translation. In some circumstances, part or all of the seat may be required to mostly translate in a single direction. A combination of the least one cam with the at least one actuator is a simple way to achieve this motion. A further advantage is that the overall operating range and capability of the at least one cam can be maximised.
Preferably, the at least one actuator comprises at least one threaded member in meshed engagement with at least one gear driven by a motor. The at least one actuator can also be a lead screw. Reinforcing elements can be located in a housing for the at least one actuator.
The seat and/or seat unit can include an aperture. The seat can then be used as a commode. In one embodiment, the seat and/or seat unit are not permanently attached to the seat frame. Preferably, the seat frame and/or the seat unit can then include a removably attached soils receptacle to sheath and enable easy emptying of the commode. The soils receptacle can have a cover to enable clean usage of the seat and reduce risk of contamination further by offering the sheath facility for one or more of the frame, seat unit and user environment with soils.
Preferably, the seat frame is mounted on wheels or sliders. This allows movement of the seat from one location to another, and allows use of the seat as, for example, a wheelchair, or alternatively to move the seat to where it is required to be used.
Preferably, when the seat frame is mounted on wheels, the raiser seat can further comprise a brake system. The brake system can be operative to prevent motion of the wheels during a lifting or lowering operation of the seat, or any other use which requires the seat to be held stable without moving, or any other use that requires the seat/frame. This can improve the safety in use of the seat.
Preferably, the brake system is associated with the movement mechanism, such that operation of the movement mechanism causes the brake system to act to prevent rotation of the wheels. This can provide a further safety advantage, by ensuring that when the movement mechanism is operated, the brake system is automatically applied.
Preferably, the at least one cam either incorporates a function reducing coating or is manufactured at least partially from a friction reducing material. In embodiment, the whole of the at least one cam is manufactured from a friction reducing material.
Preferably, the at least one cam is linked to the seat in a way which does not significantly alter the load on the movement mechanism.
In one embodiment, this is achieved by the use of a fixed connecting member (or protrusion) extending from the at least one cam. Preferably the connecting member is an extension of roller shafts of the at least one cam. The connecting member can locate within a corresponding slot in the seat and act to support the seat on the at least one cam. It can also prevent the seat from moving away from the at least one cam without significantly altering the load on the movement mechanism.
In an alternate embodiment, at least one single or double action pneumatic or hydraulic cylinder can connect the at least one cam and the seat. The cylinder can feature an orifice with dimensions chosen so as to avoid placing any further loads on the movement mechanism, yet give sufficient resistive load to prevent the seat moving away from the cam. In the event that a load is placed on the seat such that it becomes detached from the cam profile edge, the fluid within the cylinder will begin to exit the orifice at a higher rate and thus place a resistive load on the seat's movement away from the cam profile edge.
The resistive load will continue to be applied until the seat moves sufficiently far that the pneumatic cylinder is extended to the limit of its stroke, or the load case is reversed and the seat regains contact with the cam.
Preferably, the at least one cam comprises at least one of the following features: an integral gear; an integral shaft; an integral bearing; an integral bearing surface; an integral roller; a one roller assembly; at least one connection member; a roller carriage; an integrated roller carriage in whole or in part; an integral roller track; an integral seal; integral sealing surfaces or sealing area; an at least one integral location and retention component; a blade; a shaft recess; a bearing recess; a protrusion recess; an externally threaded member; an internally threaded member; one hole; one roller type or plain bearing/bush; one press fit member; one threaded member; one taper edge profile; one alternative edge profile; one increased thickness section that can run the full length of the cam; and multiple blades
More preferably, in the event that the cam comprises more than one blade, the integral location and retention component can be an area at either side of a main cam and/or the integral gear can have a different diameter, size, form or shape from that of other sections of the cam shaft.
Preferably the seat comprises a guide track adapted to receive the connecting member. In one embodiment the guide track comprises a linear track located at the side of the seat in a position where the seat is supported by the at least one cam. In another embodiment, the seat can further comprise at least one thickened material section, roller, a bearing, a friction-reducing coating, or a function reducing material, positioned along the part of the seat which is in contact with the at least one cam. If at least one roller or bearing is used, the track can be mounted on the at least one roller or bearing.
Preferably, the seat unit is removably attached to the seat frame. The attachment mechanism can include connections for electrical circuitry. These connections can be encapsulated within the seat frame. The connections can be for power, sensors, control or other functions.
Preferably, the seat frame comprises handles. The handles can be placed at various locations to allow for safe interaction with the user or operator, and allow for controlled and safe movement and location with other components and assemblies.
Preferably, the seat frame comprises footrests.